Why Are Multiple ACL Injuries So High in Younger Athletes?

Because kids are specializing in competitive sports at an increasingly early age, serious injuries typically only seen in adults are now on the rise in young athletes. This includes anterior cruciate ligament (ACL) injuries. According to a study in Pediatrics, “ACL Tears in School-Aged Children and Adolescents Over 20 Years,” there was an annual increase of 2.3% from 1994 to 2013.

But it is not just an initial ACL injury that is on the rise in young players. Surgeons are also seeing a rise in second and third ACL injuries. One recent study by Dekker et al. published in The Journal of Bone & Joint Surgery (“Return to Sport After Pediatric Anterior Cruciate Ligament Reconstruction and Its Effect on Subsequent Anterior Cruciate Ligament Injury”) reported that 84% of pediatric patients (age range, 6-17 years) were able to return to the same preinjury level of competition sport after primary reconstruction surgery, but 32% sustained a second ACL injury.

And to make matters worse, many of the athletes who undergo revision ACL reconstruction to treat a second ACL injury will go on and suffer a third injury as well. Revision surgery has been associated with a 3 or 4 times higher failure rate than primary reconstruction surgery. The why in all of this though is still not completely understood.

Some data has suggested that the presence of meniscal and chondral lesion during the revision surgery, bone tunnel management during surgery and even the rate of return to high risk sports may play a role. “Revision Anterior Cruciate Ligament Reconstruction Outcomes in Younger Patients: Medial Meniscal Pathology and High Rates of Return to Sport Are Associated With Third ACL Injuries,” a study published in the January 2018 issue of the American Journal of Sports Medicine, explored these potential risk factors for multiple ACL injuries and found that medial meniscal pathology and high return to sports (RTS) rates are the most likely culprits.

Understanding Knee Pathology

In this case-control study, 151 consecutive patients who were 25 years old or younger at time of their first revision anterior cruciate ligament (ACL) reconstruction were followed for a mean of 4.5 years (range, 2-9 years) to track the number of subsequent ACL injuries (graft re-rupture or contralateral injury to the native ACL) that occurred during this time. All of the revision ACL surgeries took place between June 2007 and July 2014 by two surgeons. Both surgical details as well as a range of sport participation outcomes were measured.

All the patients were asked to complete a survey on further injuries to the ACL-reconstructed knee and the contralateral injuries. The investigators asked the patients about the primary sport they played before the ACL injury and whether or not they returned to that sport after the primary reconstruction surgery or any subsequent surgeries. All surgical details came from the patients’ medical records.

The investigators were able to follow up with 85% (128 of the 151 patients) of the study participants. According to the data, of the 35 patients who experienced a third ACL injury, 20 experienced a graft re-rupture at a mean time of 2 years after revision surgery. Fifteen patients had contralateral ACL injuries at a mean time of 3.9 years

Kate Webster, Ph.D., an associate professor and director of sport exercise and rehabilitation research focus area at La Trobe University in Australia, and colleagues found a significant association between having medial meniscal pathology and sustaining a graft re-rupture (p = .03), but whether or not the surgeon used the same tunnels from the primary procedure at the revision surgery did not seem to be a factor. There was no association between re-rupture and whether or not new tibial or femoral bone tunnels were drilled at revision surgery (p = .8). In the group of patients who had a third ACL injury, the same bone tunnels were used for 60% of the patients compared with 63% of the patients in the group of patients who didn’t have a third ACL injury.

In addition, the investigators found no associations between graft re-rupture and lateral meniscal pathology or chondral pathology.

Returning to High Risk Sport

The researchers found, on the other hand, that the relationship between return to sport and re-ruptures was the strongest.

Investigators were able to collect return-to sport data from 119 of the 128 patients. After receiving revision reconstruction, 67% of the patients returned to their preinjury level of sport compared with 83% of the same patients after the primary reconstruction. In addition, those patients who had a third ACL injury were three times as likely to return to their pre-injury sport than those who did not have further injury (OR = 3.1; 95% of CI, 1.2-8.4).

About 65% of the athletes who had returned after revision surgery were still playing in their preinjury sport at a mean 4.5 years after surgery. Those athletes who leave their sport after initially returning after surgery did it for a number of reason including fear of a new injury (39%), physical problems with their knee (33%), and work/study commitments (28%).

Webster told OTW, “We confirmed that younger athletes are at significant risk of having multiple ACL injuries. Of the young athletes with revision ACL reconstruction in our study, 27% had a third ACL injury. This is extremely concerning for future knee health in such young athletes.”

“Our data also show that returning to high risk sport is one factor that significantly contributes to multiple ACL injuries in young athletes. We must now carefully look at the timing of return to sport in this group, and perhaps advocate that our patients wait for a longer period of time before returning. The role of return to sport criteria and prevention programs for reducing the risk of re-injury also needs to be considered.”

“This is a significant concern as young athletes who have had multiple ACL injuries by their early 20s will be at a significantly increased risk for developing knee osteoarthritis, which will have a lifetime effect on their ability to remain active.”

She added, “When patients were grouped according to whether they did or did not have a third ACL injury, those who had a third injury had the same high rate of returning to pivoting sports after the revision surgery as after their primary procedure, whereas significantly fewer patients returned to their preinjury sport in the group that did not have a third injury. This suggests that one of the reasons these patients suffered a third ACL injury was that they returned to pivoting sports. Such results clearly highlight the risk of continued exposure and the challenge of younger athletes being able to continue in their chosen sport without sustaining further injury.”

In addition, she pointed out “that 12% of patients also suffered a contralateral ACL injury may suggest that there is an intrinsic predisposition to ACL injury in some of this group as well.”

Is a New RTS Approach Needed?

Webster and her colleagues believe there is a lot more work to be done. They pointed to significant questions that still need answers. For example, should the criteria for return to sport used be based on patient’s age and type of sport? Should there be stricter guidelines for young athletes who have had multiple ACL injuries?

The investigators plan on following this group of young athletes further to get a better understanding of the effect of multiple ACL injuries at a young age.

Webster and colleagues wrote, “Ultimately, the young patient who has sustained multiple ACL injuries may need to be counseled to change from high-to-lower-risk sports, but whether this should occur after 2, 3 or even 4 injuries warrants further investigation and discussion.”

They also recommend looking closer at injury prevention programs for secondary ACL injury to see if it should include more neuromuscular training over a longer time frame than that typically used in primary injury prevention. And if so, should there be additional changes to the program if the patient has suffered a third ACL injury.

Find the full study here.